将Particle转成UGUI

在unity官方论坛看到的一个解决方案，可以将Particle直接转换成CanvasRenderer元素显示。
新建一个UIParticleSystem.cs脚本，将以下代码复制进去：

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using UnityEngine;
using UnityEngine.UI;
using System.Collections.Generic;
 
[ExecuteInEditMode]
[RequireComponent(typeof(CanvasRenderer))]
[RequireComponent(typeof(ParticleSystem))]
public class UIParticleSystem : MaskableGraphic
{
 
    public Texture particleTexture;
    public Sprite particleSprite;
 
    private Transform _transform;
    private ParticleSystem _particleSystem;
    private ParticleSystem.Particle[] _particles;
    private UIVertex[] _quad = new UIVertex[4];
    private Vector4 _uv = Vector4.zero;
    private ParticleSystem.TextureSheetAnimationModule _textureSheetAnimation;
    private int _textureSheetAnimationFrames;
    private Vector2 _textureSheedAnimationFrameSize;
 
    public override Texture mainTexture
    {
        get
        {
            if (particleTexture)
            {
                return particleTexture;
            }
 
            if (particleSprite)
            {
                return particleSprite.texture;
            }
 
            return null;
        }
    }
 
    protected bool Initialize()
    {
        // initialize members
        if (_transform == null)
        {
            _transform = transform;
        }
 
        // prepare particle system
        ParticleSystemRenderer renderer = GetComponent<ParticleSystemRenderer>();
        bool setParticleSystemMaterial = false;
 
        if (_particleSystem == null)
        {
            _particleSystem = GetComponent<ParticleSystem>();
 
            if (_particleSystem == null)
            {
                return false;
            }
 
            // get current particle texture
            if (renderer == null)
            {
                renderer = _particleSystem.gameObject.AddComponent<ParticleSystemRenderer>();
            }
            Material currentMaterial = renderer.sharedMaterial;
            if (currentMaterial && currentMaterial.HasProperty("_MainTex"))
            {
                particleTexture = currentMaterial.mainTexture;
            }
 
            // automatically set scaling
            _particleSystem.scalingMode = ParticleSystemScalingMode.Local;
 
            _particles = null;
            setParticleSystemMaterial = true;
        }
        else
        {
            if (Application.isPlaying)
            {
                setParticleSystemMaterial = (renderer.material == null);
            }
#if UNITY_EDITOR
            else
            {
                setParticleSystemMaterial = (renderer.sharedMaterial == null);
            }
#endif
        }
 
        // automatically set material to UI/Particles/Hidden shader, and get previous texture
        if (setParticleSystemMaterial)
        {
            Material material = new Material(Shader.Find("UI/Particles/Hidden"));
            if (Application.isPlaying)
            {
                renderer.material = material;
            }
#if UNITY_EDITOR
            else
            {
                material.hideFlags = HideFlags.DontSave;
                renderer.sharedMaterial = material;
            }
#endif
        }
 
        // prepare particles array
        if (_particles == null)
        {
            _particles = new ParticleSystem.Particle[_particleSystem.maxParticles];
        }
 
        // prepare uvs
        if (particleTexture)
        {
            _uv = new Vector4(0, 0, 1, 1);
        }
        else if (particleSprite)
        {
            _uv = UnityEngine.Sprites.DataUtility.GetOuterUV(particleSprite);
        }
 
        // prepare texture sheet animation
        _textureSheetAnimation = _particleSystem.textureSheetAnimation;
        _textureSheetAnimationFrames = 0;
        _textureSheedAnimationFrameSize = Vector2.zero;
        if (_textureSheetAnimation.enabled)
        {
            _textureSheetAnimationFrames = _textureSheetAnimation.numTilesX * _textureSheetAnimation.numTilesY;
            _textureSheedAnimationFrameSize = new Vector2(1f / _textureSheetAnimation.numTilesX, 1f / _textureSheetAnimation.numTilesY);
        }
 
        return true;
    }
 
    protected override void Awake()
    {
        base.Awake();
 
        if (!Initialize())
        {
            enabled = false;
        }
    }
 
    protected override void OnPopulateMesh(VertexHelper vh)
    {
#if UNITY_EDITOR
        if (!Application.isPlaying)
        {
            if (!Initialize())
            {
                return;
            }
        }
#endif
 
        // prepare vertices
        vh.Clear();
 
        if (!gameObject.activeInHierarchy)
        {
            return;
        }
 
        // iterate through current particles
        int count = _particleSystem.GetParticles(_particles);
 
        for (int i = 0; i < count; ++i)
        {
            ParticleSystem.Particle particle = _particles[i];
 
            // get particle properties
            Vector2 position = (_particleSystem.simulationSpace == ParticleSystemSimulationSpace.Local ? particle.position : _transform.InverseTransformPoint(particle.position));
            float rotation = -particle.rotation * Mathf.Deg2Rad;
            float rotation90 = rotation + Mathf.PI / 2;
            Color32 color = particle.GetCurrentColor(_particleSystem);
            float size = particle.GetCurrentSize(_particleSystem) * 0.5f;
 
            // apply scale
            if (_particleSystem.scalingMode == ParticleSystemScalingMode.Shape)
            {
                position /= canvas.scaleFactor;
            }
 
            // apply texture sheet animation
            Vector4 particleUV = _uv;
            if (_textureSheetAnimation.enabled)
            {
                float frameProgress = 1 - (particle.lifetime / particle.startLifetime);
                //                float frameProgress = textureSheetAnimation.frameOverTime.curveMin.Evaluate(1 - (particle.lifetime / particle.startLifetime)); // TODO - once Unity allows MinMaxCurve reading
                frameProgress = Mathf.Repeat(frameProgress * _textureSheetAnimation.cycleCount, 1);
                int frame = 0;
 
                switch (_textureSheetAnimation.animation)
                {
 
                    case ParticleSystemAnimationType.WholeSheet:
                        frame = Mathf.FloorToInt(frameProgress * _textureSheetAnimationFrames);
                        break;
 
                    case ParticleSystemAnimationType.SingleRow:
                        frame = Mathf.FloorToInt(frameProgress * _textureSheetAnimation.numTilesX);
 
                        int row = _textureSheetAnimation.rowIndex;
                        //                    if (textureSheetAnimation.useRandomRow) { // FIXME - is this handled internally by rowIndex?
                        //                        row = Random.Range(0, textureSheetAnimation.numTilesY, using: particle.randomSeed);
                        //                    }
                        frame += row * _textureSheetAnimation.numTilesX;
                        break;
 
                }
 
                frame %= _textureSheetAnimationFrames;
 
                particleUV.x = (frame % _textureSheetAnimation.numTilesX) * _textureSheedAnimationFrameSize.x;
                particleUV.y = Mathf.FloorToInt(frame / _textureSheetAnimation.numTilesX) * _textureSheedAnimationFrameSize.y;
                particleUV.z = particleUV.x + _textureSheedAnimationFrameSize.x;
                particleUV.w = particleUV.y + _textureSheedAnimationFrameSize.y;
            }
 
            _quad[0] = UIVertex.simpleVert;
            _quad[0].color = color;
            _quad[0].uv0 = new Vector2(particleUV.x, particleUV.y);
 
            _quad[1] = UIVertex.simpleVert;
            _quad[1].color = color;
            _quad[1].uv0 = new Vector2(particleUV.x, particleUV.w);
 
            _quad[2] = UIVertex.simpleVert;
            _quad[2].color = color;
            _quad[2].uv0 = new Vector2(particleUV.z, particleUV.w);
 
            _quad[3] = UIVertex.simpleVert;
            _quad[3].color = color;
            _quad[3].uv0 = new Vector2(particleUV.z, particleUV.y);
 
            if (rotation == 0)
            {
                // no rotation
                Vector2 corner1 = new Vector2(position.x - size, position.y - size);
                Vector2 corner2 = new Vector2(position.x + size, position.y + size);
 
                _quad[0].position = new Vector2(corner1.x, corner1.y);
                _quad[1].position = new Vector2(corner1.x, corner2.y);
                _quad[2].position = new Vector2(corner2.x, corner2.y);
                _quad[3].position = new Vector2(corner2.x, corner1.y);
            }
            else
            {
                // apply rotation
                Vector2 right = new Vector2(Mathf.Cos(rotation), Mathf.Sin(rotation)) * size;
                Vector2 up = new Vector2(Mathf.Cos(rotation90), Mathf.Sin(rotation90)) * size;
 
                _quad[0].position = position - right - up;
                _quad[1].position = position - right + up;
                _quad[2].position = position + right + up;
                _quad[3].position = position + right - up;
            }
 
            vh.AddUIVertexQuad(_quad);
        }
    }
 
    void Update()
    {
        if (Application.isPlaying)
        {
            // unscaled animation within UI
            _particleSystem.Simulate(Time.unscaledDeltaTime, false, false);
 
            SetAllDirty();
        }
    }
 
#if UNITY_EDITOR
    void LateUpdate()
    {
        if (!Application.isPlaying)
        {
            SetAllDirty();
        }
    }
#endif
 
}